This invention concerns papermaking machinery, and more particularly a texturing press for location in the press section between the Fourdrinier and drying sections of a papermaking machine.
In a known texturing press the paper, whilst still wet, is passed through the nip between two rollers at least one of which is a surface textured rubber covered roller. A problem arises in that substantial machine downtime is required to exchange the texturing roller or rollers whenever it is desired to vary the texture imparted to the paper.
It is known in the printing industry to provide a printing roller whose bearing on one side can be swung aside (to leave the roller in cantilevered condition) enabling a sleeve having an engraved rubber outer surface covering the roller to be slid axially from the roller for exchange with another which is slid axially onto the roller. In one arrangement taught by EP 0 491 802xe2x80x94A the roller is provided with a plurality of axially and circumferentially spaced apertures in its peripheral surface through which pressure air may be ejected to cause slight expansion of the sleeves and an air cushion over which they may be slid. In the arrangement of EP 0 491 802xe2x88x92A the apertures are supplied with pressure air from a common cylindrical plenum chamber beneath the outer surface of the roller.
Such a roller would not be suitable as a texturing roller on a papermaking machine because of the very much greater nip pressures of up to 1,000 lbs per linear inch (180 Kg per linear centimetre) or more involved and the greater size whereby a common air chamber within the roller shell for all of the apertures would have such volume as to require excessive air supply to obtain the needed pressures.
According to the present invention, there is provided a roller for a texturing press on a papermaking machine adapted to be fitted with an interchangeable engraved sleeve and comprising a cylindrical shell having a plurality of axially and circumferentially spaced apertures in its peripheral surface through which pressure fluid may be ejected and at least one axially extending channel within the thickness of the shell for the supply of pressure fluid to the apertures.
There may be an individual channel for each row of apertures radially inwardly of that row.
The axially extending channels may be defined by axially extending grooves in the surface of one of two roller shells which are fitted together, one inside the other.
The grooves may be in the outer peripheral surface of the inner roller shell.
The grooves may be in the inner peripheral surface of the outer roller shell.
The roller shells may be fitted together by thermally shrinking the outer shell onto the inner shell.
The axially extending channels may be defined by bores in a single roller shell.
Each aperture may be closed by a resiliently outwardly loaded valve member protruding from the surface of the roller, engagement of a sleeve with the valve member forcing same inwardly to open the aperture.
The valve member may be a ball.
The valve member may be urged outwardly by a compression spring.
The sleeves may be of plastic with an outer cover of rubber having a laser engraved textured outer surface.
The pressure fluid may be air.
Also according to the invention is a texturing press for a papermaking machine having at least one roller as aforesaid.
Also according to the invention is a papermaking machine including a texturing press as aforesaid.
The invention also includes a method of texturing paper during its production on a papermaking machine wherein texture is imparted to the paper by a texturing press as aforesaid.
The invention will be further apparent from the following description with reference to the several figures of the accompanying drawings which show a roller embodying same.